1. Field of the Invention
The present invention relates generally to the field of dental instruments and more particularly to dental wedges.
2. Related Art
Dental wedges are well known in the art and have been used in restorative dentistry for over a century. Generally, dental wedges are used to separate the teeth and hold a matrix band against the side of the tooth being restored or repaired. These functions are important for the successful restoration of the form and function of teeth. Unless adequate separation of the teeth is achieved, the adjacent teeth, once restored, will inadequately contact one another. Without adequate contact between the teeth, food will pack and otherwise accumulate in between the teeth, leading to decay and periodontal problems. Moreover, unless the matrix band conforms adequately to the side of the tooth, filling material can be forced below the gum line or leave the tooth with unnatural and irregular contours known as ledges, overhangs, and underhangs. These flaws aid and cause plaque accumulation, leading to decay and periodontal problems.
To prevent these problems, the dentist uses a wedge, which is typically piece of wood or plastic of a basic tetrahedral shape, thus tapered to a point on one end. In use, a wedge is inserted into the space between the adjacent teeth at the gum line and forced into the space to cause separation of the teeth so that they may be restored. This causes the matrix band material to be pressed against the gingival portion of the tooth at the floor of a preparation, thereby closing the space and preventing the overhang.
The ideal dental wedge should be relatively hard in order to drive the teeth apart at least the thickness of the average matrix band (approximately 0.002 inch). When the wedge and matrix band are removed, the restored teeth should rebound to their normal physiological position due to the elastic memory of the periodontal membrane and maintain physiologic contact in order to prevent food debris from packing between the teeth during chewing. The wedge should also provide resistance against the matrix band so as to prevent deformation or dislodgment due to the outward pressure a dentist typically exerts when packing restorative materials in the matrix-confined cavity space.
Most commercially available dental wedges are a basic tetrahedral shape and made of various types of wood. To accommodate different sizes of interproximal spaces, wedges are generally available in various sizes from small to large and the size used is determined by the size of the interproximal space. While these wedges are hard enough to allow the teeth to be driven apart, they suffer from the problem of not conforming adequately to the interproximal surface of the tooth.
Another basic requirement of a dental wedge is that it be able to cause the matrix band to intimately conform to the anatomical surfaces of the tooth to be restored. Often, the interproximal surface of the tooth will be concave. Wherever a dental wedge does not intimately contact the flexible matrix band and force it against the concave surface of the tooth, the band is unsupported. In such a condition, a gap or opening will develop in response to the pressure of packing the restorative material into the matrix-confined cavity preparation. These gaps allow the filling material to push past the matrix and create a ledge, overhang, or an otherwise unacceptable contour of the tooth in the interproximal space. Further, the gaps allow blood and other fluids to enter the band, thereby contaminating the restorative materials, which results in a compromised restoration as explained below. Rigid, fixed-shaped wedges or wedge type devices known in the art do not adapt well to the variable contours of the interproximal spaces.
A further problem of the present art is that the insertion of the rigid wedge is detrimental to the interproximal gingival tissues. Gingival tissue is soft and displaceable. Thus, a rigid wedge design does not accommodate the gingival tissue and simply and traumatically displaces the tissue, resulting in upward force on the teeth walls. Tearing the gingival tissue permits blood, saliva, and other contaminants to flow into the preparation cavity. Because dental restorative materials only function optimally when dry, the service and longevity of the restoration are compromised.
The dental wedge must also be easily removed from the interproximal space between the teeth. While a wedge that resists backing out is a desired characteristic of wedges, such a characteristic makes the wedge more difficult to remove from between the teeth. To accommodate placement and removal, a wedge may include a small protuberance which is adapted to be grasped by an implement such as pliers, as seen in U.S. Pat. No. 4,696,646. Easy placement and removal further reduces trauma to the gingival tissue, which results in a cleaner and drier work surface. Further, a flexible wedge that forces the band against the concavities of the interproximal tooth seals the preparation cavity against fluid seepage due to any incidental trauma that might occur.
Numerous attempts have been made to accommodate the varying interproximal surfaces of teeth, while avoiding trauma to the soft tissues and maintaining adequate stiffness to remain in place. Most dental wedges, however, share the common problem that they adhere to the basic tetrahedral shape, which on the inferior surface of the tetrahedron typically causes trauma to the gingival tissues upon surface. The wedge described in U.S. Pat. No. 3,890,714, however, includes less surface area on the side of the wedge communicating with the gingival tissue. This wedge suffers from three problems. First, the wedge body is substantially hollow, which results in ineffectual strength for conforming a matrix band to any tooth defects and insufficient strength to place the wedge and to separate the teeth. Second, the wedge does not include a protuberance for grasping the wedge with dental pliers or the like, which makes removal of the wedge particularly difficult. Third, the wedge has a tendency to back out of the interproximal space, thereby interrupting the dentist who must re-insert the wedge.